WooCommerce Event Tracking, PHP + JS

I want to track woo commerce events using a custom plugin.

I added the provided tracking code to the header using the wp_head hook, and I need to track pageviews, searches, product views...etc.

I wrote something like this,

add_action('woocommerce_single_product_summary', array(
             &$this,
            'viewed_product'
        ) , 15);

And the function :

   public function viewed_product()
    {
        $product_id = get_the_ID();
        $product = wc_get_product($product_id);
?>
    <script>
        xyz.push({
            "track"            : "productview",
            "product_id"       : <?php echo $product_id ?>,
            "product_name"     : <?php echo $product->get_name() ?>,
            "product_price"    : <?php echo $product->get_price() ?>,,
        });
    </script>
<?php

I can see that the tracking code is loaded in the header. But when I viewed the product it gives the error,

_xyz is not defined

Any solutions for this issue?